1. Field of the Invention
The present invention relates to a rip fence for use with a table saw and, in particular, to a rip fence that has a dual locking mechanism for securing the fence in position.
2. Scope of the Prior Art
Table saws of various designs include a frame and an upper surface having an opening through which a blade extends. The upper surface supports a material, such as wood, as it is pushed towards the blade for cutting. Table saws have traditionally been stand-alone pieces of equipment that are used in workshops. Because most stand-alone table saws are used in large open spaces, the dimensions of the table saw can be large enough to support materials of various sizes for cutting. Tables that are used in workshops are not readily moved from one location to another. At construction sites, it is useful to have a table saw that can be easily moved from one location to another or between different construction sites. Accordingly, smaller and portable table saws have been designed. These table saws use lighter materials and have reduced the dimensions of the frame and the upper surface to reduce the size and weight of the table saw thereby creating the desired portable table saw. The portable table saws also use a separable folding table to hold the table saw at the correct height for operation.
An integral part of most table saws is a movable rip fence. The rip fence is positioned perpendicular to the upper cutting surface and is aligned generally parallel to the position of the blade. Most rip fences are designed to span between the front edge and the rear edge of the upper cutting surface. Moreover, the rip fence can be positioned in any position along the upper surface and is secured in such a position by a locking mechanism. The rip fence is usually secured in a position a given distance away from the blade and can be put on either side of the blade. When the rip fence is secured in a position, the wood can be pushed against the side of the rip fence to slide on the upper surface to be cut by the blade. Thus, accurate and straight cuts can be made.
Rip fences of various different designs are readily known in the prior art. In addition, different methods of securing the rip fence at a given location on the upper surface, including the use of a locking mechanism, are known. One of the primary objectives for the rip fence is for it to be generally parallel to the blade so that the most accurate cuts can be made. It is known that an effective way to make the rip fence parallel with the blade is to force it to be perpendicular to the front and rear edge surfaces of the table saw. Thus, many rip fences use a front clamping mechanism and a rear clamping mechanism. The front clamping mechanism presses against the front edge surface and the rear clamping mechanism presses against the rear edge surface. In this way, the clamping mechanism aligns the rip fence perpendicular to the edge surfaces and parallel to the blade.
It is also helpful to properly align the rip fence if the front and rear clamping mechanism move simultaneously. To achieve this, rip fences typically include a handle which is connected to the front clamping mechanism and a rod that connects between the handle and the rear clamping mechanism. When the handle is in a first and released position, the front locking mechanism is positioned in a released position relative the front edge surface and the rod reduces pressure and allows the rear locking position to move into a released position relative the rear edge surface. When the handle is in a second and locked position, the front locking mechanism is positioned in a locked position along the front edge surface and the rod pushes the rear locking mechanism into the locked position. As the handle moves from the released to the locked position, the front and rear clamping mechanism engage with the front and rear edges at the same time.
Different types of front and rear locking mechanisms are known. Some front locking mechanisms include a cam that is connected to a handle such that when the handle is put into the locked position, the cam is pushed against a surface on the front edge of the table saw to secure the rip fence in position. U.S. Pat. No. 4,846,036 to Metzger, Jr., et al., reveals a handle that moves a spring-biased clamping portion. In the locked position, the clamping portion is biased against a vertical wall in a slot that is proximate the front edge surface of the upper surface. In the released position, the handle overcomes the biased clamping portion so that it is released from the wall thereby allowing the rip fence to move along the upper surface. As the rip fence moves along the upper surface, the clamping portion moves through the slot.
Other rip fences are provided with different mechanisms to move smoothly along the upper surface. As described, slots can be provided along the upper surface of the table saw through which a portion of the rip fence, like a clamping portion, can slide. In addition, tubular rails can be provided on the front and rear sides of the table saw. In those embodiments, the rip fence include a portion that surrounds the tubular rail so that the rip fence can slide into a selected position. Other types of rails can be provided underneath the upper surface. In addition, the rip fence can include hook portions, tabs or other mechanisms that move relative a part of the upper surface or the frame so that the handle can lock the rip fence in a location.
Because of the rip fences"" designs, the handles used to lock the rip fence create inefficiencies. Many such handles are quite long so that their rotation provides enough torque to adequately secure the rip fence in a selected position. Those handles often protrude significantly out from the front edge of the saw where the handle can get in the way of efficiently using the table saw. The large handles can also catch on clothing and other items. In order to reduce the size, other rip fences reorient the handle""s location on the rip fence. Other prior art methods alter the direction that the handle rotates relative the table saw. Those alternative embodiments are not as easy to use.
In view of the foregoing, it is an object of the present invention to develop a portable saw that has a rip fence to overcome the deficiencies of the prior art. What is needed is a rip fence that moves between multiple positions on the table saw, that can be secured easily in any such position, and that does not unnecessarily increase the weight or general dimensions of the table saw. It is also desired to have a rip fence that is aligned parallel to the blade when it is locked into position. Moreover, the rip fence should reduce the dimensions of the handle so that it does not protrude significantly in front of the table saw.
The present invention relates to a table saw that includes a rip fence that is slidable relative to the table saw. The table saw used with the rip fence includes a frame portion and upper cutting surface. A blade extends through an opening in the upper surface to cut wood or other material. The upper surface supports the wood as it is pushed on the table saw and cut by the blade. Front and rear edge surfaces extend perpendicularly from the front and rear edges of the upper surface.
The rip fence of the present invention can be used with a table saw that has movable auxiliary table. The auxiliary table can move between a first position adjacent the upper surface and a variable second position separated from the upper surface according to any known methods. One such method includes rails that are secured to the front and rear edge surfaces of the auxiliary table and that slide along brackets on the rear and front edge surfaces of the upper surface.
The rip fence moves between positions relative the upper surface and can be locked in any such position such that the rip fence is parallel to the blade. This arrangement ensures that accurate cuts are made. To move relative the upper surface, the rip fence engages with a slot which is parallel to the front edge surface formed on the upper cutting surface of the table saw or the upper surface of the front rail. The rip fence can also engage with an groove formed in the rear edge surface of the upper cutting surface or the outer edge of the rear rail.
The rip fence extends between the front edge surface and the back edge surface of the upper cutting surface and includes a main casing that is slightly shorter than the span of the entire rip fence. A front clamping mechanism is provided that is connected to the front end of the casing by a frame. A movable handle is pivotally connected at one end of the handle""s upper surface to the frame and rotates between a lower locked position and an upper released position. When the handle is in the locked position, the rip fence is held securely in position relative the upper cutting surface so that the rip fence is generally parallel to the blade. When the handle is in the released position, the rip fence can slide relative the upper cutting surface and longitudinally through the slot and groove.
The front clamping mechanism includes a rotatable cam that has a first end and a second end. In addition, a movable link having an upper end and a lower end is provided. The link is pivotally connected at its upper end to a distal end of the handle""s upper surface and pivotally connected at the lower end to the first end of the cam. The cam""s second end is pivotally connected to the frame. A vertically extending activating plate is partially contained within the frame such that its upper end is in contact with the cam""s second end. The lower end of the activation plate extends below the lower edge of the front clamping mechanism. The activation plate can be pivotally connected to the handle frame at a point below the upper end.
The front clamping mechanism also includes a horizontally extending clamping plate that engages with the slot. The clamping plate includes a passage proximate a first end and a flange, or lip, at an opposing second end. The lower end of the activation plate extends through the passage. The lip engages with the slot so that as the rip fence moves along the upper cutting surface the lip slides longitudinally through the passage. The lip moves laterally within the slot between a locked position and a released position. In the locked position, the lip presses against the walls of the slot so that the rip fence does not slide. In the released position, the lip is free of the slot""s walls so that the rip fence can slide to a desired position. The clamping plate moves between the locked position and the released position as the handle moves between its locked and released position. As the handle moves between positions, the link rotates the cam and therefore the activation plate. As the activation plate pivots, its lower end laterally moves the clamping plate between the locked and released positions.
The rip fence of the present invention also includes a rear clamping mechanism that has a second activation plate. An upper end of the rear activation plate is pivotally connected to a rear frame. A portion, or tab, is provided at a lower end to engage with the groove provided along the rear edge surface of the table saw. A spring-loaded rod maintains contact between the front activation plate and the upper end of the rear activation plate. The second activation plate, and therefore the portion, move between a locked position and the released position as the handle moves between those positions. As the handle moves between those positions, the first activation plate rotates about its pivot point thereby moving the rod. As the rod moves, it forces the rear activation to rotate about its pivot point so that the tab moves between the locked position and the released position. In the locked position, the edges of the portion engage with the walls of the groove so that the rip fence is secured in a position and is parallel to the blade. In the released position, the portion is removed from the groove so that the rip fence can move along the upper surface.
The front clamping mechanism, or the casing, can include gliding blocks that slide through the slot. The glide blocks are arranged on either side of the clamping plate and permit the rip fence to move smoothly through the slot between various positions. In addition, the rip fence can include a roller assembly that allows the rip fence""s rear clamping mechanism to move smoothly.
In view of the foregoing, a rip fence is provided that moves smoothly between various positions along the upper cutting surface. The multiple pivot points in the front clamping mechanism also provide a handle that is easy to use and that does not protrude out from the table saw. The clamping plate and rear activation plate also provide effective mechanisms to secure the rip fence in a position so that the rip fence does not move during operations of the table saw. In addition, the front and rear clamping mechanisms align the rip fence in a generally parallel arrangement with the blade when they are moved into the locked position.
These and numerous other features and advantages of the present invention will become readily apparent from the following description, the accompanying drawings and the appended claims.